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Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D″ layer


The Earth's lower mantle is believed to be composed mainly of (Mg,Fe)SiO3 perovskite, with lesser amounts of (Mg,Fe)O and CaSiO3 (ref. 1). But it has not been possible to explain many unusual properties of the lowermost 150 km of the mantle (the D″ layer) with this mineralogy. Here, using ab initio simulations and high-pressure experiments, we show that at pressures and temperatures of the D″ layer, MgSiO3 transforms from perovskite into a layered CaIrO3-type post-perovskite phase. The elastic properties of the post-perovskite phase and its stability field explain several observed puzzling properties of the D″ layer: its seismic anisotropy2, the strongly undulating shear-wave discontinuity at its top3,4,5,6 and possibly the anticorrelation between shear and bulk sound velocities7,8.

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Figure 1: Structure of the post-perovskite phase of MgSiO3 (calculated at 120 GPa).
Figure 2: Stability of the post-perovskite phase.
Figure 3: Experimental powder diffraction pattern at 118 GPa and 300 K matching the predicted lattice parameters.


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Calculations were performed at CSCS (Manno) and ETH Zurich. We thank P. Ulmer, A.N. Halliday, S. Goes, F. Cammarano, A.B. Thompson and P.J. Tackley for discussions, and Y. Ohishi and N. Sata for experimental support. Synchrotron radiation experiments were performed at the BL10XU, SPring-8.

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Correspondence to Artem R. Oganov.

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Oganov, A., Ono, S. Theoretical and experimental evidence for a post-perovskite phase of MgSiO3 in Earth's D″ layer. Nature 430, 445–448 (2004).

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